Raster is a data format consisting of regular grids of values, usually stored in an image-like format.

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How to set the value of a pixel based on its current value?

I am attempting to set the value of a pixel based on its current value. I am using the Raster Calculator in Quantum GIS dev 1.7 trunk. For example, if the value is 0, I want to set it to 255. Based ...
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1answer
901 views

GRASS - Will r.to.vect work on this scanned map?

Total GRASS noob here. I have several very large hand contoured maps to digitize, and this thread intrigues me. In the past I have spent hours upon hours digitizing these maps and revisions in ArcMap. ...
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1answer
297 views

Two rasters created from the same polygon have different extents?

My problem is that i am trying to export some rasters to Rockworks so that i can create a sand layer from them. Rockworks requires the grid files i use to have the exact same XY co-ordinates. So i ...
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1answer
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Count of raster cells as variable in arcgis 10 modelbuilder

I want to use a cell count of an integer raster as a variable in Arcgis 10 modelbuilder (and later in a python script), but can't seem to find how to access this information. Is there a (python) ...
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1answer
249 views

How to export a png file from a raster file? r.out.png has an error

I used r.out.png to export a png file, but it produced this error: (Sun Feb 27 00:26:32 2011) r.out.png input=raster_bulacanElevation ...
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1answer
746 views

Is there a way of cutting a raster map that is displayed in the GRASS GIS Map Display?

I have a raster map that I generated from cropping/masking from a bigger raster map. It produced a map with only a portion of not null values. I only want to have a map that is zoomed in to the ...
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Difference between Geoserver stores: ImageMosaic, WorldImage, ImagePyramid

What are the differences between the Geoserver stores ImageMosaic, WorldImage, and ImagePyramid? I noticed that ImagePyramid is no longer included in the latest Geoserver. Is one of these more ...
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1answer
419 views

Extract many or clustered cells attributes around points

My question is similar to Extract raster values at points, but perhaps more complex. How to extract the attributes of clustered cells around a point/points? For example, I have many vegetation plots ...
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R: Download a large DEM, change projection, and adjust to smaller scale

This is a process that takes just a few seconds in GIS software. My attempt to do it in R uses a large amount of memory then fails. Is there something wrong in my code, or is this just something R ...
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2answers
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R: overlay a line on a raster stack/brick, and get profile of cell values along the line

I've combed through R's raster functions and vignettes and can't seem to get this working. I want to specify a line/vector across a raster stack (a DEM and possibly related variables), and get a ...
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1answer
179 views

gdalwarp results all black

I'm trying to convert a bmp image in BNG to WGS84 using gdalwarp (via QGIS). It seems to be running without errors but the output is all black. What am I doing wrong?
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Combining Two Adjacent Raster Datasets

I am trying to figure out how to combine two adjacent rasters into one raster using ArcMAP 9.3.1. The problem I am having is that there appears to be a gap in the data. I would like to be able to ...
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1answer
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Watershed Delineation

I am trying to delineate just the catchment area of some lakes, and am wondering the correct way to do this. I already have a filled DEM, along with a flow direction and a flow accumulation raster. Is ...
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3answers
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Creating a raster surface of overlaps from vector polygon shapefiles?

Basically what I'm trying to do (in ArcGIS 10) is to compare three vector files in order to create a 'comparison' raster layer. I tried using Data Comparison (under Data Management tools) but it ...
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2answers
763 views

Help with a Simple Code to Read a Metadata from a Raster File

Please help me with a python code to read metadata from a Raster file. Thanks
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0answers
642 views

two results of IDW in ArcMAP are different

i added the following points to ArcMAP using "Add XY Data". x,y,z 7,39,117 27,17,122 27,61,123 46,36,136 52,14,138 55,46,141 56,56,137 65,24,144 65,36,145 Changed raster output size in "options" ...
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1answer
254 views

How to write binary ArcGRIDs outside of ArcGIS in linux?

I've been looking for a way to create\write binary formatted ArcGRID images in Linux without much luck. It seems the GDAL project only supports reading these files, but there is not write support. ...
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1answer
235 views

Creating color table file in PCI Geomatica

What is the simplest way to create a stand-alone color-table file in PCI Geomatica (PCT or STR)? I have some classified imagery with values ranging between 0-255 and I would like a way to ...
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1answer
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How do I get the count of NoData values in a raster?

I have created a raster in ArcGIS 10 with a large number of holes (NoData) in it. I want to fill the holes using something like the the following: rOut = arcpy.sa.Con(arcpy.sa.IsNull(rGround), ...
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3answers
715 views

How to get the elevation of the areas in a raster file from SRTM?

I have an SRTM elevation map. How do I get the elevation of each point in the map? I am using GRASS. Is there a GRASS script to do such?
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1answer
373 views

How to get the Flow or directional raster map using GRASS?

Aside from using r.fill.dir in GRASS, is this the script to produce the Flow or directional raster map? Is this the output for the script ...
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1answer
877 views

How to select a raster file that is under a polygon in a vector file?

I am using: v.db.select map=PHL_adm1 where=NAME_1='Bulacan' My vector map is over the raster map. I want to select the part of the raster map under the polygon(NAME_1='Bulacan') of a vector. Is it ...
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1answer
1k views

How to combine a vector and a raster file?

I want to combine a raster and a vector file. After combining, can I query on the resulting map to obtain a specific area? How?
3
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1answer
339 views

Converting dataset between coordinate systems

I'm working with NOAA's PRECipitation REConstruction over Land dataset, and am looking for an efficient way to sample the data by pixels on NASA's MODIS grid, using open source tools. The PRECL data ...
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1answer
104 views

Non-Research Transportation Raster applications

My experience with rasters is pretty basic. 99.95% of what I do involves vector and transportation modelling. In research, there are numerous transportation applications using rasters and imagery ...
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1answer
458 views

How to sensibly digitise this raster, scriptably, in ArcGIS

I have the raster below which I want to convert to a set of vector lines: As you can see, there are small breaks in the lines and some bits are double-width. I want to be able to reliably import ...
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2answers
603 views

Scriptable alternative to ArcScan (particularly vectorising lines within tolerances)

Sadly the answer to this question suggests that it is not possible to script ArcScan from within a python script. Therefore, does anyone know of any alternatives to ArcScan (either within ArcGIS, or ...
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2answers
1k views

Converting google map api coordinates into meters

How would I go about converting the results of my map bounding box into meters within javascript? For example, if I have the coordinates 51.52366625446907, -0.07467269897460938 decimal degrees, can I ...
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Statistical relationships between rasters

I am trying to analyze how sets of rasters relate to each other using some statistical techniques. As, I don't have much experience using the spatial statistics tools in ArcGIS I was exporting my ...
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213 views

Process to gather raster cells under features

I need to gather individual raster cells underneath a feature in a featureclass as quickly as possible. It seems that most ArcObjects functions have problem with island polygons, multi-part polygons, ...
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3answers
1k views

raster not displaying below certain scale

i've clipped a raster in 20 smaller images and i can zoom in until 1:150 in the original raster but, in the smaller ones, when i go below 1:4000, the workspace goes blank. i'm working with arcgis 9.3 ...
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Clipping a raster using a polyline or polygon

I have a large raster created from values that cover the whole United States and Alaska which are both polygon and polyline features, this raster was caluclated using Spatial Analyst IDW ...
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699 views

Find the best path along raster

I've just posted a question to StackOverflow about the best way to go about finding the best path on the raster below (where whiter pixels are 'better'), but have realised that it might actually be ...
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How do I use GDAL to convert from an arbitrary projection/datum into Equirectangular/WGS84?

I've been trying to use GDAL to convert from an arbitrary projection/datum into Equirectangular (aka Plate Caree, aka Equidistant Cylindrical, aka Geographic, aka Lat/Long) with WGS84 datum. All of ...
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1answer
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How can I compute raster pixel width and height given raster bounds, row count, and column count?

Restated, how do I convert arc degrees to meters? For example, I have an elevation data raster that has the following metadata: WEST LONGITUDE=64.97798789° E NORTH LATITUDE=33.02003415° N EAST ...
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1answer
675 views

Good Java-Based Raster Libraries

Can anyone suggest a good, Java-based raster library? By good, I mean a library that can read common raster formats (ex. tif, img...etc) and save them to other image formats (ex. png). I say ...
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7answers
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Extract raster values at points

How can I extract values from a raster by points. I prefer not in Arcgis. I prefer in Qgis or Mapwindow or other open source gis.
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265 views

What practices are available for modelling land suitability?

I currently use a "classic" raster based approach of dividing a study area into cells. All input layers are converted to rasters at the same cell resolution and given a suitability rating. A final ...
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Delivering map tiles in real-time without caching? [closed]

I am wondering how useful would you find to have a way to deliver map tiles quickly over the web without worrying about caching or seeding them? With raster map engines we know that this is a ...
6
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2answers
855 views

Moving raster to different mapset GRASS GIS

I have a raster DEM that I created in one mapset but I would like to copy it to another mapset for another purpose. Is this possible within GRASS or can I just copy some files over in the ...
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6answers
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Creating simple image from vector data

Can anyone suggest a quick (and preferably open source) way to create an image from a shapefile. For example, I have a shapefile containing parcel boundaries, I want to create a png file depicting ...
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1answer
451 views

How to Save a Raster or Polygon to ArcMap Table of Contents in C#?

Just as the title says, I want to save the Raster to the table of contents. I have a Raster displaying on the ArcMap IDisplay, but I can't figure out how to save it to the Table of Contents in ...
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8answers
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What raster-based GIS systems really work?

Raster GISes like GRASS, ArcGIS/Spatial Analyst, and Idrisi can perform a rich set of data processing and analytical procedures loosely known as "map algebra." In today's computing environment it is ...
14
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1answer
839 views

Are there any general rules of thumb for selecting a transformation for Georeferencing?

There are several transformations that can be used when georeferencing a raster: 1st order Polynomial (affine) 2nd order Polynomial 3rd order Polynomial Spline... etc Are there any specific rules ...
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4answers
13k views

How do you decide what interpolation method to use for resampling raster data?

The question pretty much says it all; are there hard and fast rules about which interpolation methods are suited to each kind of raster data? Any Golden rules, rules of thumb? Good books or articles ...
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How can I access a raster dataset's attribute table?

I need to loop through the rows in the raster attribute table and add a date for each row. Thanks,
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1answer
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Coordinates of upper left corner in the world file?

According to Wikipedia and ESRI last two lines in the world file represent x and y coordinates of center of upper left pixel. Now, if I have a world file like this: 32.0 0.0 0.0 -32.0 691200.0 ...
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4answers
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Quantum GIS and ECW images?

How might I enable Quantum GIS to read ECW imagery? At the moment I'm mostly concerned about this on Ubuntu 10.4 amd64, but I also use WinXP & Win7.
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2answers
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Unrestricted codec for creating raster files with interior pyramids files

I'm looking for a tool that will allow me to mosaic a collection of images into a file format with performance similar to MrSID or ECW, but without the licensing restrictions that those formats come ...
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1answer
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How to resample a batch of rasters using OGR/GDAL?

I'm looking for a function similar to GRASS r.resample. I have a folder full of TIF files and want to reduce their resolution ("scale them down") to reduce file size.